This invention is concerned with modular plastic conveyor belts, and particularly with an improved method for transferring articles from a plastic conveyor belt made up of segments or modules.
In many conveyor belt applications, there is a need to transfer items or materials from one conveyor belt to another surface. One typical approach is to place the conveyor belt at a higher level than the other surface, and merely allow items to fall from the belt as the belt passes over a sprocket or roller, so that the items fall onto the surface below. Unfortunately, in many applications this approach cannot be used because the items or materials to be transferred are fragile and can be damaged by the fall.
Another approach to transferring items at the end of a conveyor run is to place a transfer support surface adjacent to and approximately level with the downstream end of the conveyor run, at the point of the belts return over a roller or a row of sprockets. Unfortunately, such a method is generally only applicable to large items because the gap between the transfer support surface and the belt will vary as the flat surfaced belt segments or modules round the sprocket or roller. As a result of the gap's opening and closing, smaller items can slip through the space or clog the space.
In U.S. Pat. No. 4,051,949 there is shown and described a modular conveyor belt and fingered comb combination for transferring articles to and from a conveyor belt. A similar system is shown in U.S. Pat. No. 5,083,659. In both these patents, an open link modular belt is provided with relatively high, linear topped vertical ribs or finger plates which extend along each module in the direction of movement of the belt. These ribs or ridges form axial passageways down the surface of the belt, through which teeth of the transfer comb, located at the end of the conveyor belt run, can extend. As the belt passes through the transfer comb, items on the belt are smoothly transferred from the conveyor belt surface to the surface of the comb. The patent discloses a module configuration intended to minimize the rise and fall of the vertical plates as the belt passes over the sprocket or roller. A problem with such a system is that the teeth on the transfer comb have a tendency to break off, and the module plates are also somewhat fragile.
A principal object of this invention is to provide an open link conveyor belt transfer system capable of moving articles on or off the belt with as little disturbance as possible, while at the same time avoiding the need for transfer combs. The invention is directed to overcoming the shortcomings of the transfer methods and apparatus set forth above, with a simple transfer method which was not contemplated in previous conveyor systems.
Several patents have disclosed arched-top links in conveyor belts and in that sense are relevant to the present invention. Furbush U.S. Pat. No. 1,769,992 shows a conveyor for use with sticky or pasty material, particularly for a drying operation. The links are formed with arched tops so as to pass around sprockets at the end of the conveyor run in a cylindrical form. This configuration was disclosed for the purpose of helping effect transfer of the conveyed material; however, transfer is accomplished not smoothly onto a platform, but with a rotatable beater and rotatable brush, both of which remove the conveyed material and clean any material which might stick to the conveyor.
Livermore U.S. Pat. No. 4,542,821 is relevant in that it discloses a "humpback conveyor" which forms a cylindrical surface on passing over a sprocket, and which employs a "doctor blade" for cleaning the surface of the conveyor as it passes over the sprocket (FIG. 1). The conveyor is disclosed as being for use in food processing where material may adhere to and may need to be cleaned from the surface of the belt. The belt is formed of metal links which extend throughout the width of the belt, rather than being in modules each of which is of lesser width than the composite belt. The "doctor blade" shown in the Livermore patent is a steeply inclined scraper blade positioned at the cylindrical surface formed by the links as they pass over the sprocket; the blade is strictly for cleaning residual material off the belt, not for purposes of transfer.
Ball U.S. Pat. No. 2,693,268, also showing a conveyor formed of full-width links which apparently are of metal, shows transfer of conveyed material using a scraper blade with a knife edge, substantially contacting the cylindrical surface of the arched-top links as they pass around a sprocket or roller. The patent discusses the advantage of the arched-top link configuration as enabling discharge to an adjacent conveyor without relying on a significant elevation difference between the conveyors. As in other prior conveyor belts of this nature, Ball shows a belt which is not open but which is closed to the maximum extent possible to prevent particles from falling down through the conveyor, being designed for handling loose materials such as coal particles which could clog and jam in the conveyor.
The following additional patents show conveyor belts having some pertinence to this invention: Bode U.S. Pat. No. 5,083,659, Fesler U.S. Pat. No. 5,121,831, Garvey U.S. Pat. No. 4,351,429, Burpee U.S. Pat. No. 1,224,445 (disclosing in column 1 but not illustrating a "stationary deflector" for removing fish from the belt), Hyatt U.S. Pat. No. 786,903 and Dodge U.S. Pat. No. 685,115.
The present applicant has also produced and sold a modular, open-link conveyor belt, the width of which was made up of two or more plastic modules, the links having arched tops, for use in the sewage treatment industry and not as a transfer device. The belt has been used with a scraper blade contacting the arched tops of the links as they pass around an end roller, presenting a cylindrical surface, the scraper blade being strictly for the purpose of scraping the belt clean and not being arranged as a transfer platform. It is the method of using such a belt for smooth transfer of conveyed products, which is the subject of this invention.